1. Field of the Invention
The present invention relates to a mobile phone, and more particularly to a method for minimizing transmission power deviations of channels in a mobile phone.
2. Description of the Related Art
Typically, a mobile phone uses particular channels for mobile phone services allocated thereto. For instance, 20 channels are allocated as available channels for cellular mobile communications in Korea. These available channels are selected from advanced mobile phone service (AMPS) channels. The AMPS channel numbers of such available channels are 1011, 29, 70, 111, 152, 193, 234, 275, 316, 363, 404, 445, 486, 527, 568, 609, 650, 697, 738, and 779.
Transmission power for each available channel in a mobile phone should meet a specifically made standard tolerance. In a mobile phone, however, transmission power may vary among different channels even at the same automatic gain control (AGC) level because the frequency characteristics of the radio frequency (RF) module used in the mobile phone may vary among those channels. Furthermore, even in the case of mobile phones of the same model manufactured by the same manufacturer, a difference in transmission power may exist for the same channel because those mobile phones have different hardware characteristics. Transmission power variations among different channels or transmission power differences among different phones for the same channel are called xe2x80x9ctransmission power deviations of channelsxe2x80x9d. When the transmission power deviations of channels is high, errors in transmission power such as generation of maximum power or an open loop on a certain channel may occur.
In order to minimize such transmission power deviations of channels, the manufacturer may conduct, for each phone manufactured, a measurement of transmission power for each available channel while varying the AGC level, and then adjust the transmission power for each available channel to an optimal level, based on the measured transmission power. In this case, transmission AGC levels corresponding to the optimal transmission power are stored in a non-volatile memory and they are used for available channels during a practical use of the phone set. For the non-volatile memory, an electrically erasable and programmable ROM (EEPROM) is typically used.
However, a lot of time is taken for the above mentioned method in which transmission AGC levels are obtained by conducting, for each phone, a measurement of transmission power for all available channels, which are typically 20 in number, and then conducting an adjustment of transmission power based on the measured transmission power. Each transmission AGC level relevant to available channels is stored in a non-volatile memory. As a result, the non-volatile memory area in use increases according to the number of available channels.
In order to reduce the above mentioned problem, a method is proposed in which adjustment channels are used, the number of which is less than the number of available channels. That is, optimum transmission AGC level values are derived only for the adjustment channels, and then stored in the non-volatile memory of the portable phone. Using these stored AGC level values, the optimum transmission power of available channels for a mobile hone may be determined when the mobile phone is used in practice. The determination of optimum transmission power is made only for the currently available channel, based on the stored transmission AGC level values. This is because the current available channel may vary in optimum transmission power depending on the characteristics of the phone hardware. Thus, the number of channels for which certain processes are required in the process of manufacturing mobile phones is reduced. These processes include measuring transmission power, adjusting the transmission power, deriving transmission AGC levels of those channels in association with the adjusted transmission power, and storing the derived transmission AGC levels in a non-volatile memory. Accordingly, the above process is simplified, thereby reducing the above mentioned problems.
However, when this method is used, it is necessary to accurately and efficiently adjust or compensate for the transmission AGC levels stored in the non-volatile memory for the currently available channel. If not, high transmission power deviations of channels may result in errors in transmission power in practical use even though the problems involved in the manufacture of the mobile phone are eliminated.
One object of the present invention is to provide a method for minimizing transmission power deviations of channels. Another object of the present invention is to provide a method for efficiently compensating for transmission power deviations.
In accordance with the present invention, this object is accomplished by providing a method for compensating transmission power deviations of channels in a mobile phone using adjustment channels selected from channels for mobile phone service, while including a reference channel allocated to the mobile phone from the channels for mobile phone service, the number of adjustment channels being less than the number of the allocated available channels, the mobile phone including an non-volatile memory stored with respective transmission automatic gain control (AGC) level values for the adjustment channels derived in accordance with an adjustment for transmission power to an optimum level for each of the adjustment channels, comprising:
an offset value processing procedure for reading out the transmission AGC level values from the non-volatile memory, and deriving offset values corresponding to respective differences between the transmission AGC level value of the reference channel and respective transmission AGC level values of the remaining adjustment channels; and
a compensation value processing procedure for deriving a compensation value for a currently available channel, based on the offset values of adjustment channels located above and below the currently available channel, the channel span between the currently available channel and the adjustment channel located below it, and the channel span between the adjustment channels located above and below the currently available channel, while using the following expression:       ch_pwr    ⁢    _offset    =                              (                                    max_ch              ⁢              _offset                        -                          min_ch              ⁢              _offset                                )                span            xc3x97              (                  ch          -          min_ch                )              +          min_ch      ⁢      _offset      
where xe2x80x9cch_pwr_offsetxe2x80x9d represents the compensation value, xe2x80x9cmax_ch_offsetxe2x80x9d and xe2x80x9cmin_ch_offsetxe2x80x9d represent the offset values of the adjustment channels located above and below the currently available channel respectively; xe2x80x9cspanxe2x80x9d represents the channel span between the adjustment channel located above the available channel and the adjustment channel located below the available channel, xe2x80x9cchxe2x80x9d represents the channel number of the currently available channel, and xe2x80x9cmin_chxe2x80x9d represents the channel number of the adjustment channel located below the available channel. The adjustment channel above the currently available channel is the xe2x80x9cupper limit adjustment channelxe2x80x9d and the adjustment channel below is the xe2x80x9clower limit adjustment channelxe2x80x9d.